The ‘love hormone’ not only triggers emotions when you see your beloved but also helps old muscles work like new.

According to new research, oxytocin – a hormone associated with maternal nurturing, social attachments, childbirth and sex – is indispensable for healthy muscle maintenance and repair.

“Our quest was to find a molecule that not only rejuvenates old muscle and other tissue but that can do so sustainably without increasing the risk of cancer,” said principal investigator Irina Conboy, an associate professor of bioengineering at University of California, Berkeley.

Conboy and her research team found that oxytocin is a good candidate because it is a broad range hormone that reaches every organ and is not known to be associated with tumours or to interfere with the immune system.

“This is the hormone that makes your heart melt when you see kittens, puppies and human babies,” said Conboy.

The new study determined that in mice, blood levels of oxytocin declined with age.

To tease out oxytocin’s role in muscle repair, the researchers injected the hormone under the skin of old mice for four days, and then for five days more after the muscles were injured.

After the nine-day treatment, they found that the muscles of the mice that had received oxytocin injections healed far better than those of a control group of mice without oxytocin.

“The action of oxytocin was fast. The repair of muscle in the old mice was at about 80 percent of what we saw in the young mice,” Conboy added.

The researchers also found that blocking the effects of oxytocin in young mice rapidly compromised their ability to repair muscle, which resembled old tissue after an injury.

They noted that oxytocin could become a viable alternative to hormone replacement therapy and for long-term health.

In addition to healthy muscle, oxytocin is predicted to improve bone health and combat obesity, said the study published in the journal Nature Communications.